I'm using a service called Simplify Media that scans your music folders or iTunes libraries so you can stream your music to/from other computers or to/from your iPhone or iPod Touch.
You can add friends so you can share music between computers, so anyone wanna share? I can invite you if you're interested and don't have an account.
I would love to get in on that, does it work for Mac?
Yup, and Linux. Either post or PM me your e-mail address.
I've got upwards of 15k songs and it's indexed 5,500 in 20 minutes or so, so it's pretty quick. Plus I'm using it mainly on my iPhone and over WiFi it plays songs instantly and over 3G it takes about 3 seconds to start streaming, which I was impressed with.
Now I can keep my 14GBs of space for stuff other than music, like my converted porn collection. D